One of the very few "director's cut" editions that improved a film was Blade Runner, and that mostly by taking things out (Ford's awful voiceover, demanded by the studio and recorded basically under duress).
"Dark City" and "Troy" are also vastly improved by the director's cut.
"Amadeus" has one pivotal scene restored that improves the film, and one scene that doesn't, and several little bits of dialogue that were better off remaining trimmed.
This is the same scenario with the Untitled edition of ALMOST FAMOUS. Lots of good character stuff with Patrick Fugit and Kate Hudson, but also scenes that just don't work, and one inclusion that outright ruins one of the best moments of comic timing in the film.
"That Thing You Do" has an extra 40 minutes in their director's cut, it's more of an extended version with a lot more Charlize Theron and a bunch of extra neat stuff that absolutely slowed the movie down a ton but is fun to see put back in.
The Director's Cut of Kingdom of Heaven adds roughly that much material as well, including a (pretty important) character that was edited out of the theatrical release entirely.
